Resonance Searches With The T Overline T Invariant Mass Distribution Measured With The D O Experiment At Sqrt S
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Resonance Searches With The T Overline T Invariant Mass Distribution Measured With The D O Experiment At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2010
Resonance Searches With The T Overline T Invariant Mass Distribution Measured With The D O Experiment At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
Understanding the universe, its birth and its future is one of the biggest motivations in physics. In order to understand the cosmos, the fundamental particles forming the universe, the components our matter is built of need to be known and understood. Over time physicists have built a theory which describes the physics of the known fundamental particles very well: the Standard Model (SM) of particle physics. The SM describes the particles, their interactions and phenomena with high precision. So far no proven deviations from the SM have been found, though recently evidence for possible physics beyond the SM has been observed. The SM is not describing the mass of the elementary particles however and even with the addition of the Higgs mechanism giving mass to the particles, we have no full theory for all four fundamental forces. We know the model needs to be extended or replaced by another one, as gravitation is not included in the SM. Having a theory which describes all fundamental particles found so far and all but one fundamental interaction is a great success. However, all this describes about 4% of the universe we live in. 23% is dark matter and 73% is dark energy. Dark matter is believed to interact only through gravity and maybe the weak force, which makes it hardly observable. Dark energy is even more elusive. Among other theories the cosmologic constant and scalar fields are discussed to describe it. One should also note that other models exist which for example modify the Newtonian law of gravity. The Higgs mechanism has become the most popular model for mass generation. Alternative theories like Super Symmetry (SUSY), large Extra Dimensions, Technicolor, String Theory, to name just a few, have spread to describe the necessary mass generation or new particles. As proof for new physics beyond the SM has not been found yet, one assumes that new physics will manifest itself at a larger energy scale and therefore a higher particle mass. Particles with high masses are therefore presumed to be a window to test the SM for deviations caused by new physics. The heaviest fundamental particle which is in our reach is the top quark. Its mass is almost as large as that of a complete tungsten atom. It is so heavy, that it decays faster than it can hadronize. It seems the perfect probe to study new physics at the moment. In this analysis the top quark is used as a probe to search for a new resonance, whose properties are similar to a SM Z boson but is much more massive. This analysis will study t{bar t} decays to search for an excess in the invariant mass distribution of the t{bar t} pairs. Resonant states are suggested for massive Z-like bosons in extended gauge theories, Kaluza Klein states of the gluon or Z, axigluons, topcolor, and other beyond the Standard Model theories. Independent of the exact model a resonant production mechanism should be visible in the t{bar t} invariant mass distribution. In this thesis a model-independent search for a narrow-width heavy resonance X decaying into t{bar t} is performed. In the SM, the top quark decays into a W boson and a b quark nearly 100% of the time, which has been proven experimentally, too. The t{bar t} event signature is fully determined by the W boson decay modes. In this analysis, only the lepton+jets final state, which results from the leptonic decay of one of the W bosons and the hadronic decay of the other, is considered. The event signature is an isolated electron or muon with high transverse momentum, large transverse energy imbalance due to the undetected neutrino, and at least three jets, two of which result from the hadronization of b quarks.
Resonance Searches With The T Bar T Invariant Mass Distribution Measured With The D Experiment At U221a S
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Author :
language : en
Publisher:
Release Date : 2010
Resonance Searches With The T Bar T Invariant Mass Distribution Measured With The D Experiment At U221a S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
Understanding the universe, its birth and its future is one of the biggest motivations in physics. In order to understand the cosmos, the fundamental particles forming the universe, the components our matter is built of need to be known and understood. Over time physicists have built a theory which describes the physics of the known fundamental particles very well: the Standard Model (SM) of particle physics. The SM describes the particles, their interactions and phenomena with high precision. So far no proven deviations from the SM have been found, though recently evidence for possible physics beyond the SM has been observed. The SM is not describing the mass of the elementary particles however and even with the addition of the Higgs mechanism giving mass to the particles, we have no full theory for all four fundamental forces. We know the model needs to be extended or replaced by another one, as gravitation is not included in the SM. Having a theory which describes all fundamental particles found so far and all but one fundamental interaction is a great success. However, all this describes about 4% of the universe we live inches 23% is dark matter and 73% is dark energy. Dark matter is believed to interact only through gravity and maybe the weak force, which makes it hardly observable. Dark energy is even more elusive. Among other theories the cosmologic constant and scalar fields are discussed to describe it. One should also note that other models exist which for example modify the Newtonian law of gravity. The Higgs mechanism has become the most popular model for mass generation. Alternative theories like Super Symmetry (SUSY), large Extra Dimensions, Technicolor, String Theory, to name just a few, have spread to describe the necessary mass generation or new particles. As proof for new physics beyond the SM has not been found yet, one assumes that new physics will manifest itself at a larger energy scale and therefore a higher particle mass. Particles with high masses are therefore presumed to be a window to test the SM for deviations caused by new physics. The heaviest fundamental particle which is in our reach is the top quark. Its mass is almost as large as that of a complete tungsten atom. It is so heavy, that it decays faster than it can hadronize. It seems the perfect probe to study new physics at the moment. In this analysis the top quark is used as a probe to search for a new resonance, whose properties are similar to a SM Z boson but is much more massive. This analysis will study t{bar t} decays to search for an excess in the invariant mass distribution of the t$\bar{t}$ pairs. Resonant states are suggested for massive Z-like bosons in extended gauge theories, Kaluza Klein states of the gluon or Z, axigluons, topcolor, and other beyond the Standard Model theories. Independent of the exact model a resonant production mechanism should be visible in the t$\bar{t}$ invariant mass distribution. In this thesis a model-independent search for a narrow-width heavy resonance X decaying into t$\bar{t}$ is performed. In the SM, the top quark decays into a W boson and a b quark nearly 100% of the time, which has been proven experimentally, too. The t$\bar{t}$ event signature is fully determined by the W boson decay modes. In this analysis, only the lepton+jets final state, which results from the leptonic decay of one of the W bosons and the hadronic decay of the other, is considered. The event signature is an isolated electron or muon with high transverse momentum, large transverse energy imbalance due to the undetected neutrino, and at least three jets, two of which result from the hadronization of b quarks.
Resonance Searches With The Tt Invariant Mass Distribution Measured With The D Experiment At S
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Author : Thorsten D. Schliephake
language : en
Publisher:
Release Date : 2010
Resonance Searches With The Tt Invariant Mass Distribution Measured With The D Experiment At S written by Thorsten D. Schliephake and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
Resonance Searches With The Tt Invariant Mass Distribution Measured With The D Experiment At S
DOWNLOAD
Author : Thorsten D. Schliephake
language : en
Publisher:
Release Date : 2010
Resonance Searches With The Tt Invariant Mass Distribution Measured With The D Experiment At S written by Thorsten D. Schliephake and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
Search For Resonances In Diphoton Events At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2016
Search For Resonances In Diphoton Events At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
Searches for new resonances decaying into two photons in the ATLAS experiment at the CERN Large Hadron Collider are described. The analysis is based on proton-proton collision data corresponding to an integrated luminosity of 3.2 fb-1 at √s = 13 TeV recorded in 2015. Two searches are performed, one targeted at a spin-2 particle of mass larger than 500 GeV, using Randall-Sundrum graviton states as a benchmark model, and one optimized for a spin-0 particle of mass larger than 200 GeV. Varying both the mass and the decay width, the most significant deviation from the background-only hypothesis is observed at a diphoton invariant mass around 750 GeV with local significances of 3.8 and 3.9 standard deviations in the searches optimized for a spin-2 and spin-0 particle, respectively. The global significances are estimated to be 2.1 standard deviations for both analyses. As a result, the consistency between the data collected at 13 TeV and 8 TeV is also evaluated. Limits on the production cross section times branching ratio to two photons for the two resonance types are reported.
Search For Narrow Resonances In Dilepton Mass Spectra In Proton Proton Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2016
Search For Narrow Resonances In Dilepton Mass Spectra In Proton Proton Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
A search for narrow resonances in dielectron and dimuon invariant mass spectra has been performed using data obtained from proton-proton collisions at $ \sqrt{s} = $ 13 TeV collected with the CMS detector. The integrated luminosity for the dielectron sample is 2.7 fb$^{-1}$ and for the dimuon sample 2.9 fb$^{-1}$. The sensitivity of the search is increased by combining these data with a previously analysed set of data obtained at $ \sqrt{s} = $ 8 TeV and corresponding to a luminosity of 20 fb$^{-1}$. No evidence for non-standard-model physics is found, either in the 13 TeV data set alone, or in the combined data set. Upper limits on the product of production cross section and branching fraction have also been calculated in a model-independent manner to enable interpretation in models predicting a narrow dielectron or dimuon resonance structure. Limits are set on the masses of hypothetical particles that could appear in new-physics scenarios. For the $\mathrm{Z}'_{\text{SSM}}$ particle, which arises in the sequential standard model, and for the superstring inspired $\mathrm{Z}'_{\psi}$ particle, 95% confidence level lower mass limits for the combined data sets and combined channels are found to be 3.37 and 2.82 TeV, respectively. The corresponding limits for Kaluza-Klein gravitons arising in the Randall-Sundrum model of extra dimensions with coupling parameters 0.01 and 0.10 are 1.46 and 3.11 TeV, respectively. These results significantly extend previous limits.
Resonances From Two Universal Extra Dimensions
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Author :
language : en
Publisher:
Release Date : 2006
Resonances From Two Universal Extra Dimensions written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with categories.
Standard model gauge bosons propagating in two universal extra dimensions give rise to heavy spin-1 and spin-0 particles. The lightest of these, carrying Kaluza-Klein numbers (1,0), may be produced only in pairs at colliders, whereas the (1,1) modes, which are heavier by a factor of (square root)2, may be singly produced. We show that the cascade decays of (1,1) particles generate a series of closely-spaced narrow resonances in the t{bar t} invariant mass distribution. At the Tevatron, s-channel production of (1,1) gluons and electroweak bosons will be sensitive to t{bar t} resonances up to masses in the 0.5-0.7 TeV range. Searches at the LHC for resonances originating from several higher-level modes will further test the existence of two universal extra dimensions.
Search For Narrow Resonances In Dijet Final States At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2016
Search For Narrow Resonances In Dijet Final States At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
A search for narrow resonances decaying into dijet final states is performed on data from proton-proton collisions at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 18.8 fb-1. The data were collected with the CMS detector using a novel technique called data scouting, in which the information associated with these selected events is much reduced, permitting collection of larger data samples. This technique enables CMS to record events containing jets at a rate of 1 kHz, by collecting the data from the high-level-trigger system. In this way, the sensitivity to low-mass resonances is increased significantly, allowing previously inaccessible couplings of new resonances to quarks and gluons to be probed. The resulting dijet mass distribution yields no evidence of narrow resonances. Upper limits are presented on the resonance cross sections as a function of mass, and compared with a variety of models predicting narrow resonances. Furthermore, the limits are translated into upper limits on the coupling of a leptophobic resonance Z'B to quarks, improving on the results obtained by previous experiments for the mass range from 500 to 800 GeV.
Search For A New Resonance Decaying Into Top Antitop At Tevatron
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Author : Christian Schwanenberger
language : en
Publisher:
Release Date : 2006
Search For A New Resonance Decaying Into Top Antitop At Tevatron written by Christian Schwanenberger and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with categories.
In this report a new search for a narrow-width heavy resonance decaying into top quark pairs (X {yields} t{bar t}) in p{bar p} collisions at {radical}s = 1.96 TeV has been performed using data collected by the D0 detector at the Fermilab Tevatron collider. The analysis considers t{bar t} candidate events in the lepton+jets channel using a lifetime tag to identify b-jets and the t{bar t} invariant mass distribution to search for evidence of resonant production. The analyzed dataset corresponds to an integrated luminosity of approximately 370 pb{sup -1}. Since no evidence for a t{bar t} resonance X is found, upper limits on {sigma}{sub x} x B(X {yields} t{bar t}) for different hypothesized resonance masses using a Bayesian approach are set. Within a topcolor-assisted technicolor model, the existence of a leptophobic Z' boson with M{sub Z'}
Search For Dijet Resonances In Sqrt S
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Author : Sing Leung Cheung
language : en
Publisher:
Release Date : 2011
Search For Dijet Resonances In Sqrt S written by Sing Leung Cheung and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.